鄂尔多斯盆地镇北地区长4+5段沉积储层特征

Sedimentary Reservoir Characteristics of Chang 4+5 Member in Zhenbei Area,Ordos Basin

通过野外露头、岩心观察,铸体薄片、阴极发光、扫描电镜和常规压汞等分析测试方法,对镇北地区长4+5段沉积储层特征进行了综合详细的研究。结果表明镇北地区长4+5段主要发育辫状河三角洲前缘及三角洲平原两种沉积亚相,共发育6~8条主要水下分流河道。该区砂岩岩性以灰白色、浅灰绿色中-细的岩屑长石砂岩与长石岩屑砂岩为主,其次为岩屑砂岩,其储集空间以粒间孔为主,长石溶孔及岩屑溶孔次之;孔隙类型以复合型呈现,以发育粒间孔-溶孔为主,其中Ⅱ类孔喉组合为主要类型。该区储层孔隙度均值为11.89%,渗透率均值为1.75×10^(-3)μm^(2),其属于特低孔、特低渗油藏。长4+5段储层成岩作用以机械压实、胶结及溶蚀作用为主,其中I/S比为25%-35%,属于中成岩A期。通过沉积储层特征的研究将对研究区产建开发工作提供理论指导意义。

The sedimentary reservoir characteristics of Chang 4+5 member in Zhenbei area were comprehensively and detailedly studied by means of field outcrop,core observation,casting thin section,cathodoluminescence,scanning electron microscope and conventional mercury intrusion.The results show that two sedimentary subfacies,braided river delta front and delta plain,are mainly developed in Chang 4+5 member of Zhenbei area,and 6~8 main underwater distributary channels are developed.The lithology of sandstone in this area is mainly grayish white and light grayish green medium fine lithic arkose and feldspathic lithic sandstone,followed by lithic sandstone.Its reservoir space is dominated by intergranular pores,fol-lowed by feldspar dissolution pores and lithic dissolution pores;The pore type is composite type,mainly developing intergranular pore dissolved pore,of which the type II pore throat combination is the main type.The average porosity of the reservoir in this area is 11.89%,and the average permeability is 1.75×10^(-3)μm^(2),which belongs to low porosity and ultra-low permeability reservoir.The diagenesis of Chang 4+5 reservoir is dominated by mechan-ical compaction,cementation and dissolution,in which the I/S ratio is 25%~35%,belonging to the middle diagenesis stage A.The study of sedimen-tary reservoir characteristics will provide theoretical guidance for the production,construction and development of the study area.